Tricyclic compounds as MRP1-inhibitors

ABSTRACT

The present invention relates to a compounds of formula I, wherein A is olefin, diol, or acetonide; which are useful for inhibiting resistant neoplasms where the resistance is conferred in part or in total by MRP1.

This is the national phase application, under 35 USC 371, forPCT/US01/16475 filed Jun. 1, 2001 now U.S. Ser. No. 01/96346, whichclaims the priority of 60/211,430, filed Jun. 14, 2000.

Along with surgery and radiotherapy, chemotherapy continues to be aneffective therapy for many cancers. In fact, several types of cancer arenow considered to be curable by chemotherapy and include Hodgkin'sdisease, large cell lymphoma, acute lymphocytic leukemia, testicularcancer and early stage breast cancer. Other cancers such as ovariancancer, small cell lung and advanced breast cancer, while not yetcurable, are exhibiting positive response to combination chemotherapy.

One of the most important unsolved problems in cancer treatment is drugresistance. After selection for resistance to a single cytotoxic drug,cells may become cross resistant to a whole range of drugs withdifferent structures and cellular targets, e.g., alkylating agents,antimetabolites, hormones, platinum-containing drugs, and naturalproducts. This phenomenon is known as multidrug resistance (MDR). Insome types of cells, this resistance is inherent, while in others, suchas small cell lung cancer, it is usually acquired.

Such resistance is known to be multifactorial and is conferred by atleast two proteins: the 170 kDa P-glycoprotein (MDR1) and the morerecently identified 190 kDa multidrug resistance protein (MRP1).Although both MDR1 and MRP1 belong to the ATP-binding cassettesuperfamily of transport proteins, they are structurally very differentmolecules and share less than 15% amino acid homology. Despite thestructural divergence between the two proteins, by 1994 there were noknown consistent differences in the resistance patterns of MDR1 and MRP1cell lines. However, the association, or lack thereof, of MRP1 andresistance to particular oncolytics is known. See Cole, et. al.,“Pharmacological Characterization of Multidrug Resistant MRP-transfectedHuman Tumor Cells”, Cancer Research, 54:5902-5910, 1994. Doxorubicin,daunorubicin, epirubicin, vincristine, and etoposide are substrates ofMRP1, i.e., MRP1 can bind to these oncolytics and redistribute them awayfrom their site of action, the nucleus, and out of the cell. Id andMarquardt, D., and Center, M. S., Cancer Research, 52:3157, 1992.

Doxorubicin, daunorubicin, and epirubicin are members of theanthracycline class of oncolytics. They are isolates of various strainsof Streptomyces and act by inhibiting nucleic acid synthesis. Theseagents are useful in treating neoplasms of the bone, ovaries, bladder,thyroid, and especially the breast. They are also useful in thetreatment of acute lymphoblastic and myeloblastic leukemia, Wilm'stumor, neuroblastoma, soft tissue sarcoma, Hodgkin's and non-Hodgkin'slymphomas, and bronchogenic carcinoma.

Vincristine, a member of the vinca alkaloid class of oncolytics, is anisolate of a common flowering herb, the periwinkle plant (Vinca roseaLinn). The mechanism of action of vincristine is still underinvestigation but has been related to the inhibition of microtubuleformation in the mitotic spindle. Vincristine is useful in the treatmentof acute leukemia, Hodgkin's disease, non-Hodgkin's malignant lymphomas,rhabdomyosarcoma, neuroblastoma, and Wilm's tumor.

Etoposide, a member of the epipodophyllotoxin class of oncolytics, is asemisynthetic derivative of podophyllotoxin. Etoposide acts as atopoisomerase inhibitor and is useful in the therapy of neoplasms of thetestis, and lung.

Additionally, PCT publications WO99/51236, WO99/51228, and WO99/51227disclose certain compounds known to be inhibitors of MRP1.

It is presently unknown what determines whether a cell line will acquireresistance via a MDR1 or MRP1 mechanism. Due to the tissue specificityof these transporters and/or in the case where one mechanismpredominates or is exclusive, it would be useful to have a selectiveinhibitor of that one over the other. Furthermore, when administering adrug or drugs that are substrates of either protein, it would beparticularly advantageous to coadminister an agent that is a selectiveinhibitor of that protein. It is, therefore, desirable to providecompounds, which are selective inhibitors of MDR1 or MRP1.

The present invention relates to a compound of formula I:

where:

or

Y is —E—C(O)R¹ or —E—NR²R³;

E is a bond or —CH₂—;

R¹ is independently at each occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈cycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, optionally substituted heterocycle, or NR²R⁴;

R² is independently at each occurrence hydrogen, C₁-C₆ alkyl, (C₁-C₆alkyl)-aryl, or aryl;

R³ is independently at each occurrence hydrogen, C₁-C₆ alkyl, C₁-C₄alkoxy, optionally substituted heterocycle, optionally substituted C₃-C₈cycloalkyl, optionally substituted C₆-C₁₀ bicycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, C(O)C(O)R⁹, C(O)R⁵, or R² and R³,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle;

R⁴ is independently at each occurrence hydrogen, C₁-C₆ alkyl, C₁-C₄alkoxy, optionally substituted C₃-C₈ cycloalkyl, optionally substitutedC₆-C₁₀ bicycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl,optionally substituted aryl, optionally substituted (C₁-C₄alkyl)-heterocycle, optionally substituted heterocycle, or R² and R⁴,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle;

R⁵ is independently at each occurrence C₁-C₆ alkyl, C₁-C₆ alkoxy, (C₁-C₄alkoxy)-aryl, (C₁-C₄ alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃,optionally substituted (C₁-C₄ alkyl)-(C₃-C₈ cycloalkyl), optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl,diphenylmethyl, optionally substituted (C₁-C₄ alkyl)—CO-aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, optionally substituted (C₁-C₄ alkyl)-phenoxy,(CH₂)_(t)C(R⁶)(R⁷)N(R⁶)(R⁸), or NR²R⁴;

t is 0, 1, 2, 3, or 4;

R⁶ is independently at each occurrence hydrogen or C₁-C₆ alkyl;

R⁷ is independently at each occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈cycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, or optionally substituted heterocycle;

R⁸ is independently at each occurrence hydrogen, C₁-C₆ alkyl, optionallysubstituted C₃-C₈ cycloalkyl, optionally substituted C₆-C₁₀bicycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, optionally substituted (C₁-C₄ alkyl)-heterocycle,optionally substituted heterocycle, C(O)OR⁹, C(O)R¹⁰, or R⁶ and R⁸,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle;

R⁹ is independently at each occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈cycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, or optionally substituted heterocycle;

R¹⁰ is independently at each occurrence C₁-C₆ alkyl, C₁-C₆ alkoxy,(C₁-C₄ alkoxy)-aryl, (C₁-C₄ alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃,optionally substituted (C₁-C₄ alkyl)-(C₃-C₈ cycloalkyl), optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl,diphenylmethyl, optionally substituted (C₁-C₄ alkyl)—CO-aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, or optionally substituted (C₁-C₄ alkyl)-phenoxy, or apharmaceutical salt thereof.

The present invention further relates to a method of inhibiting MRP1 ina mammal which comprises administering to a mammal in need thereof aneffective amount of a compound of formula I, or a pharmaceutical salt orsolvate thereof.

In another embodiment, the present invention relates to a method ofinhibiting a resistant neoplasm, or a neoplasm susceptible to resistancein a mammal which comprises administering to a mammal in need thereof aneffective amount of a compound of formula I, or a pharmaceutical salt orsolvate thereof, in combination with an effective amount of an oncolyticagent.

The present invention also relates to a pharmaceutical formulationcomprising a compound of formula I, or a pharmaceutical salt or solvatethereof, in combination with one or more oncolytics, pharmaceuticalcarriers, diluents, or excipients therefor.

The present invention relates to a product containing a compound offormula I and one or more oncolytic agents as a combined preparation forsimultaneous, separate or sequential use in cancer therapy.

In another embodiment, the present invention relates to a use of acompound of formula I as defined in claim 1 in the manufacture of amedicament for inhibiting MRP1.

The current invention concerns the discovery that a select group ofcompounds, those of formula I, are selective inhibitors of multidrugresistant protein (MRP1) and are thus useful in treating MRP1 conferredmultidrug resistance (MDR) in a resistant neoplasm and a neoplasmsusceptible to resistance.

The terms “inhibit” as it relates to MRP1 and “inhibiting MRP1” refer toprohibiting, alleviating, ameliorating, halting, restraining, slowing orreversing the progression of, or reducing MRP1's ability to redistributean oncolytic away from the oncolytic's site of action, most often theneoplasm's nucleus, and out of the cell.

As used herein, the term “effective amount of a compound of formula I”refers to an amount of a compound of the present invention which iscapable of inhibiting MRP1. The term “effective amount of an oncolytic”refers to an amount of oncolytic capable of inhibiting a neoplasm,resistant or otherwise.

The term “inhibiting a resistant neoplasm, or a neoplasm susceptible toresistance” refers to prohibiting, halting, restraining, slowing orreversing the progression of, reducing the growth of, or killingresistant neoplasms and/or neoplasms susceptible to resistance.

The term “resistant neoplasm” refers to a neoplasm, which is resistantto chemotherapy where that resistance is conferred in part, or in total,by MRP1. Such neoplasms include, but are not limited to, neoplasms ofthe bladder, bone, breast, lung(small-cell), testis, and thyroid andalso includes more particular types of cancer such as, but not limitedto, acute lymphoblastic and myeloblastic leukemia, Wilm's tumor,neuroblastoma, soft tissue sarcoma, Hodgkin's and non-Hodgkin'slymphomas, and bronchogenic carcinoma.

A neoplasm, which is “susceptible to resistance”, is a neoplasm whereresistance is not inherent nor currently present but can be conferred byMRP1 after chemotherapy begins. Thus, the methods of this inventionencompass a prophylactic and therapeutic administration of a compound offormula I.

The term “chemotherapy” refers to the use of one or more oncolyticswhere at least one oncolytic is a substrate of MRP1. A “substrate ofMRP1” is an oncolytic that binds to MRP1 and is redistributed away fromthe oncolytics site of action, (the neoplasm's nucleus) and out of thecell, thus, rendering the therapy less effective.

The terms “treat” or “treating” bear their usual meaning which includespreventing, prohibiting, alleviating, ameliorating, halting,restraining, slowing or reversing the progression, or reducing theseverity of MRP1 derived drug resistance in a multidrug resistant tumor.

In the general formulae of the present document, the general chemicalterms have their usual meanings. For example, the term “C₁-C₄ alkyl”refers to methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl,cyclobutyl, s-butyl, and t-butyl. The term “C₁-C₆ alkyl” refers to amonovalent, straight, branched, or cyclic saturated hydrocarboncontaining from 1 to 6 carbon atoms and includes C₁-C₄ alkyl groups. Inaddition, C₁-C₆ alkyl also includes, but is not limited to, cyclopentyl,pentyl, hexyl, cyclohexyl, and the like. The term “C₃-C₈ cycloalkyl”refers to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,and cyclooctyl. The term “C₆-C₁₀ bicycloalkyl” refers tobicyclo-[2.1.1]hexanyl, [2.2.1]heptanyl, [3.2.1]octanyl, [2.2.2]octanyl,[3.2.2]nonanyl, [3.3.1]nonanyl, [3.3.2]decanyl, and [4.3.1]decanyl ringsystem where the ring is connected to the parent molecular moiety at anypoint available for substitution on the ring.

The terms “C₁-C₄ alkoxy” and “C₁-C₆ alkoxy” refer to moieties of theformula O—(C₁-C₄ alkyl) and O—(C₁-C₆ alkyl) respectively.

The term “optionally substituted C₃-C₈ cycloalkyl” refers to a C₃-C₈cycloalkyl optionally substituted once with a phenyl, substitutedphenyl, hydroxy, or C₁-C₄ alkoxy.

The term “halo” or “halide” refers to fluoro, chloro, bromo, and iodo.

The term “aryl” refers to phenyl, benzyl, and naphthyl.

The term “optionally substituted (C₁-C₄ alkyl)-phenoxy” refers tounsubstituted or substituted phenoxy linked through an optionallysubstituted C₁-C₄ alkyl.

The terms “optionally substituted C₁-C₄ alkyl” and “optionallysubstituted C₁-C₆ alkyl” refers to a C₁-C₄ alkyl or C₁-C₆ alkyl,respectively, unsubstituted or substituted from 1 to 3 times with halo,C₁-C₄ alkanol, NH₂, or hydroxy.

The term “optionally substituted (C₁-C₄ alkyl)-heterocycle” refers tooptionally substituted heterocycle linked through an optionallysubstituted C₁-C₄ alkyl.

The term “N-heterocycle” refers to a nitrogen containing heterocyclelinked through a nitrogen atom.

The term “optionally substituted (C₁-C₄ alkyl)-aryl” refers tooptionally substituted aryl linked through an optionally substitutedC₁-C₄ alkyl.

The term “optionally substituted (C₁-C₄ alkyl)—CO-aryl” refers to anoptionally substituted aryl linked through a carbonyl and an optionallysubstituted C₁-C₄ alkyl.

The terms “optionally substituted aryl” refers to an aryl groupoptionally substituted from 1 to 5 times independently with C₁-C₆ alkyl,halo, hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, ortrifluoromethoxy.

The terms “optionally substituted phenyl” refers to a phenyl groupoptionally substituted from 1 to 5 times independently with C₁-C₆ alkyl,halo, hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, ortrifluoromethoxy.

The terms “optionally substituted C₆-C₁₀ bicycloalkyl” refers to aC₆-C₁₀ bicycloalkyl group optionally substituted from 1 to 5 timesindependently with C₁-C₆ alkyl, halo, hydroxy, trifluoromethyl, C₁-C₆alkoxy, benzyloxy, or trifluoromethoxy.

The term “heterocycle” is taken to mean stable aromatic and non-aromatic5- and 6-membered rings containing from 1 to 3 heteroatoms selected fromthe group consisting of nitrogen, oxygen and sulfur, said rings beingoptionally benzofused. Non-aromatic rings include, for example,pyrrolidinyl, piperidinyl, piperazinyl, tetrahydrofuryl, oxazolidinyl,dioxanyl, pyranyl, and the like. Benzofused non-aromatic rings includeindolinyl, 1,2,3,4-tetrahydroquinolinyl, 1,2,3,4-tetrahydroisoquinolinyland the like. Aromatic rings include furyl, thienyl, pyridinyl,pyrrolyl, N-methylpyrrolyl, oxazolyl, isoxazolyl, pyrazolyl, imidazolyl,triazolyl, oxadiazolyl, thiadiazolyl, thiazolyl, pyrimidinyl, pyrazinyl,pyridazinyl, and the like. Benzofused aromatic rings includeisoquinolinyl, benzoxazolyl, benzthiazolyl, quinolinyl, benzofuranyl,thionaphthyl, indolyl and the like.

The term “optionally substituted heterocycle” refers to a heterocyclering optionally substituted 1 or 2 times independently with a C₁-C₆alkyl, halo, benzyl, phenyl, trifluoromethyl, or an oxo group.

The term “optionally substituted N-heterocycle” refers to a heterocyclering, linked through the nitrogen atom, optionally substituted 1 or 2times independently wit a C₁-C₆ alkyl, halo, benzyl, phenyl,trifluoromethyl, or an oxo group.

The term “protecting group” refers to an amino protecting group or ahydroxy protecting group. The species of protecting group will beevident from whether the “Pg” group is attached to a nitrogen atom(amino protecting group) or attached to an oxygen atom (hydroxyprotecting group).

The term “amino protecting group” as used in this specification refersto a substituent(s) of the amino group commonly employed to block orprotect the amino functionality while reacting other functional groupson the compound. Examples of such amino-protecting groups include theformyl group, the trityl group, the phthalimido group, the acetyl group,the trichloroacetyl group, the chloroacetyl, bromoacetyl, and iodoacetylgroups, urethane-type blocking groups such as benzyloxycarbonyl,9-fluorenylmethoxycarbonyl (“FMOC”), and the like; and like aminoprotecting groups. The species of amino protecting group employed is notcritical so long as the derivatized amino group is stable to thecondition of subsequent reaction(s) on other positions of the moleculeand can be removed at the appropriate point without disrupting theremainder of the molecule. Similar amino protecting groups used in thecephalosporin, penicillin, and peptide arts are also embraced by theabove terms. Further examples of groups referred to by the above termsare described by T. W. Greene, “Protective Groups in Organic Synthesis”,John Wiley and Sons, New York, N.Y., 1991, Chapter 7 hereafter referredto as “Greene”. A preferred amino protecting group ist-butyloxycarbonyl.

The term “hydroxy protecting group” denotes a group understood by oneskilled in the organic chemical arts of the type described in Chapter 2of Greene. Representative hydroxy protecting groups include, forexample, ether groups including methyl and substituted methyl ethergroups such as methyl ether, methoxymethyl ether, methylthiomethylether, tert-buylthiomethyl ether, (phenyldimethylsilyl)methoxy-methylether, benzyloxymethyl ether, p-methoxybenzyloxy-methyl ether, andtert-butoxymethyl ether, substituted ethyl ether groups such asethoxyethyl ether, 1-(2-chloroethoxy)-ethyl ether,2,2,2-trichloroethoxymethyl ether, and 2-(trimethylsilyl)ethyl ether,isopropyl ether groups; phenyl and substituted phenyl ether groups suchas phenyl ether, p-chlorophenyl ether, p-methoxyphenyl ether, and2,4-dinitrophenyl ether, benzyl and substituted benzyl ether groups suchas benzyl ether, p-methoxybenzyl ether, o-nitrobenzyl ether, and2,6-dichlorobenzyl ether; and alkylsilyl ether groups such astrmethyl-triethyl- and triisopropylsilyl ethers, mixed alkylsilyl ethergroups such as dimethylisopropylsilyl ether, and diethylisopropylsilylether, and ester protecting groups such as formate ester, benzylformatester, mono- di- and trichloroacetate esters, phenoxyacetate ester, andp-chlorophenoxyacetate and the like. The species of hydroxy protectinggroup employed is not critical so long as the derivatized hydroxy groupis stable to the conditions of subsequent reaction(s) on other positionsof the intermediate molecule and can be selectively removed at theappropriate point without disrupting the remainder of the moleculeincluding any other hydroxy protecting group(s).

The term “carbonyl activating group” refers to a substituent of acarbonyl that renders that carbonyl prone to nucleophilic addition.Suitable activating groups are those that have a net electronwithdrawing effect on the carbonyl. Such groups include, but are notlimited to, alkoxy, aryloxy, nitrogen containing aromatic heterocycles,or amino groups such as oxybenzotriazole, imidazolyl, nitrophenoxy,pentachlorophenoxy, N-oxysuccinimide, N,N′-cyclohexylisoure-O-yl,N-hydroxy-N-methoxyamino, and the like; acetates, formates, sulfonatessuch as methanesulfonate, ethanesulfonate, benzenesulfonate, orp-toluenylsulfonate, and the like; and halides especially chloride,bromide, or iodide.

In general, the term “pharmaceutical” when used as an adjective meanssubstantially non-toxic to living organisms. For example, the term“pharmaceutical salt” as used herein, refers to salts of the compoundsof formula I which are substantially non-toxic to living organisms. See,e.g., Berge, S. M, Bighley, L. D., and Monkhouse, D. C., “PharmaceuticalSalts”, J. Pharm. Sci., 66:1, 1977. Typical pharmaceutical salts includethose salts prepared by reaction of the compounds of formula I with aninorganic or organic acid or base. Such salts are known as acid additionor base addition salts respectively. These pharmaceutical saltsfrequently have enhanced solubility characteristics compared to thecompound from which they are derived, and thus are often more amenableto formulation as liquids or emulsions.

Examples of pharmaceutical acid addition salts are the sulfate,pyrosulfate, bisulfate, sulfite, bisulfite, phosphate,monohydrogenphosphate, dihydrogenphosphate, metaphosphate,pyrophosphate, chloride, bromide, iodide, acetate, propionate,decanoate, caprylate, acrylate, formate, isobutyrate, caproate,heptanoate, propiolate, oxalate, malonate, succinate, suberate,sebacate, fumarate, maleate, butyne-1,4-dioate, hexyne-1,6-dioate,benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate,hydroxybenzoate, methoxybenzoate, phthalate, sulfonate, xylenesulfonate,phenylacetate, phenylpropionate, phenylbutyrate, citrate, lactate,γ-hydroxybutyrate, glycollate, tartrate, methanesulfonate,ethanesulfonate, propanesulfonate, naphthalene-1-sulfonate,napththalene-2-sulfonate, mandelate, and the like of a compound offormula I.

Examples of pharmaceutical base addition salts are the ammonium,lithium, potassium, sodium, calcium, magnesium, methylamino,diethylamino, ethylene diamino, cyclohexylamino, and ethanolamino salts,and the like of a compound of formula I.

The term “solvate” represents an aggregate that comprises one or moremolecules of the solute, such as a formula I compound, with one or moremolecules of solvent The compounds of the present invention may,depending upon their structure and manner of synthesis and isolation,exist as a pharmaceutically acceptable solvate. These solvates includewater, methanol, and ethanol. Solvated forms of the compounds of thepresent invention represent a further embodiment of the presentinvention.

The term “suitable solvent” refers to a solvent that is inert to theongoing reaction and sufficiently solubilizes the reactants to effectthe desired reaction. Examples of suitable solvents include but are notlimited to, dichloromethane, chloroform, 1,2-dichloroethane, diethylether, acetonitrile, ethyl acetate, 1,3-dimethyl-2-imidazolidinone,tetrahydrofuran, dimethylformamide, toluene, chlorobenzene,dimethylsulfoxide, mixtures thereof, and the like.

The term “carbonyl activating reagent” refers to a reagent that convertsthe carbonyl of a carboxylic acid group to one that is more prone tonucleophilic addition and includes, but is not limited to, such reagentsas those found in “The Peptides”, Gross and Meienhofer, Eds., AcademicPress (1979), Ch. 2 and M. Bodanszky, “Principles of Peptide Synthesis”,2^(nd) E, Springer-Verlag Berlin Heidelberg, 1993, hereafter referred toas “The Peptides” and “Peptide Synthesis” respectively. Specifically,carbonyl activating reagents include nucleophilic sources of a halogensuch as, thionyl bromide, thionyl chloride, oxalyl chloride, and thelike; alcohols such as nitrophenol, pentachlorophenol, and the like;amines such as N-hydroxy-N-methoxyamine and the like; acid halides suchas acetic, formic, methanesulfonic, ethanesulfonic, benzenesulfonic, orp-tolylsulfonic acid halide, and the like; and compounds such as1,1′-carbonyldiimidazole, benzotriazole, imidazole,N-hydroxysuccinimide, dicyclohexylcarbodiimide, and the like.

The term “suitable thermodynamic base” refers to a base which acts as aproton trap for any protons which may be produced as a byproduct of thedesired reaction or to a base which provides a reversible deprotonationof an acidic substrate and is reactive enough to effect the desiredreaction without significantly effecting any undesired reactions.Examples of thermodynamic bases include, but are not limited to,carbonates, bicarbonates, and hydroxides (e.g., lithium, sodium, orpotassium carbonate, bicarbonate, or hydroxide), tri-(C₁-C₄alkyl)amines, or aromatic nitrogen containing heterocycles (e.g.,pyridine).

The term “hydroxy protecting group” denotes a group understood by oneskilled in the organic chemical arts of the type described in Chapter 2of T. W. Greene, “Protective Groups in Organic Synthesis”, John Wileyand Sons, New York, N.Y., 1991, hereafter referred to as “Greene”.Representative hydroxy protecting groups include, for example,dihydropyran, ether groups including methyl and substituted methyl ethergroups such as methyl ether, methoxymethyl ether, methylthiomethylether, tert-buylthiomethyl ether, (phenyldimethylsilyl)methoxy-methylether, benzyloxymethyl ether, p-methoxybenzyloxy-methyl ether, andtert-butoxymethyl ether, substituted ethyl ether groups such asethoxyethyl ether, 1-(2-chloroethoxy)ethyl ether,2,2,2-trichloroethoxymethyl ether, and 2-(trimethylsilyl)ethyl ether;isopropyl ether groups; phenyl and substituted phenyl ether groups suchas phenyl ether, p-chlorophenyl ether, p-methoxyphenyl ether, and2,4-dinitrophenyl ether, benzyl and substituted benzyl ether groups suchas benzyl ether, p-methoxybenzyl ether, o-nitrobenzyl ether, and2,6-dichlorobenzyl ether, and alkylsilyl ether groups such astrimethyl-triethyl- and triisopropylsilyl ethers, mixed alkylsilyl ethergroups such as dimethylisopropylsilyl ether, and diethylisopropylsilylether, and ester protecting groups such as formate ester, benzylformateester, mono-, di-, and trichloroacetate esters, phenoxyacetate ester,and p-chlorophenoxyacetate and the like. Further examples of groupsreferred to by the above terms are described by “Greene”. The species ofhydroxy protecting group employed is not critical so long as thederivatized hydroxy group is stable to the conditions of subsequentreaction(s) on other positions of the intermediate molecule and can beselectively removed at the appropriate point without disrupting theremainder of the molecule including any other hydroxy protectinggroup(s).

While all of the compounds of the present invention are useful, certainof the compounds are particularly interesting and are preferred. Thefollowing listing sets out several groups of preferred compounds,formulations, and methods. It will be understood that each of thelistings may be combined with other listings to create additional groupsof preferred embodiments.

1) A is the olefin;

2) A is the diol;

3) A is the acetonide;

4) A is trans substituted;

5) A is cis substituted;

6) E is a bond;

7) Y is —E—NR²R³;

8) When Y is —E—NR²R³, R³ is hydrogen;

9) When Y is —E—NR²R³, R³ is aryl;

10) When Y is —E—NR²R³, R³ is optionally substituted aryl;

11) When Y is —E—NR²R³, R³ is C(O)R⁵;

12) When Y is —E—NR²R³, R³ is C(O)R⁵, R⁵ is C₁-C₆ alkyl;

13) When Y is —E—NR²R³, R³ is C(O)R⁵, R⁵ is optionally substituted(C₁-C₄ alkyl)-aryl;

14) When Y is —E—NR²R³, R³ is C(O)R⁵, R⁵ is optionally substituted aryl;

15) When Y is —E—NR²R³, R³ is C(O)R⁵, R⁵ is (CH₂)_(t)C(R⁶)(R⁷)N(R⁶)(R⁸);

16) The compounds of the examples;

17) The compound is a pharmaceutical salt; and

18) The compound is the hydrochloride salt.

The compounds of the present invention can be prepared by a variety ofprocedures, some of which are illustrated in the Schemes below. Theparticular order of steps required to produce the compounds of formula Iis dependent upon the particular compound being synthesized, thestarting compound, and the relative lability of the substitutedmoieties.

Compounds of formula I(a) may be prepared from compounds of formula IIas illustrated in Scheme 1 below where Y and A are as described supra.

Compounds of formula I may be prepared by dissolving or suspending acompound of formula II in a suitable solvent, preferablydimethylformamide, and adding a suitable base, including potassiummethoxide, potassium tert-butoxide, potassium carbonate, sodiumhexamethyldisilazane, and preferably potassium hexamethyldisilazane. Thebase is typically employed in an one to one ratio. However, as theskilled artisan would appreciate, a slight molar excess, usually inabout a 1.1 to about a 3 fold molar excess relative to the compound offormula II is acceptable.

The reactants are typically combined at a temperature from about 0° C.to about 100° C., preferably from about 50° C. to about 60° C. Thereactants are preferably combined at room temperature and the resultingsolution is typically mixed for from about 5 minutes to about 18 hours,preferably from about 3 hours to about 6 hours.

Any protecting groups remaining in the cyclized compound of formula Imay be removed as taught in Greene to provide the compounds of formulaI. Preferred choices of protecting groups and methods for their removalmay be found in the Preparations and Examples sections below.

Compounds of formula I may also be prepared by palladium chemistrymethods as generally described in Preparations 3, 6 and 8. The salt formof the tricycle (see Route 1 infra for synthesis of the tricyclic salt)is added to an appropriate ester derivative of the olefin form of A inthe presence of an appropriate catalyst, as is illustrated inPreparation 3. This alcohol is further converted to the ester by methodswell known in the art, see for example preparation 4. The ester is thenconverted to the protected amide by methods will known in the art, seefor example preparation 5. The amide may be further converted tocompounds of formula I by general organic chemistry techniques, seeExamples 1-7.

The starting materials and compounds of the present invention may beobtained by a number of routes. For example, compounds of formula II maybe prepared according to the routes shown in Schemes 2-5.

Where Y and A are as described supra, compounds of formula II may beprepared according to Scheme 2.

Compounds of formula XI may be converted to the corresponding acidhalide by methods well known to one skilled in the art. Compounds offormula II may be prepared by dissolving or suspending an acid halide ofa compound of formula XI in a suitable solvent and adding a compound offormula i in a suitable solvent. Triethylamine or dimethylformamide areconvenient solvents and are typically preferred for the compound offormula XI. A 1:1 mixture of DMF and dichloromethane is a convenientsolvent mixture and is typically preferred for the amine of formula i.This amide forming reaction is also preferably run in the presence of4dimethylaminopyridine (DMAP).

DMAP is employed in a catalytic fashion. For example, about 5 molarpercent to about 15 molar percent, relative to the compound of formulai, is typically employed. A 10 molar percent is usually preferredCompounds of formula i; wherein the amino groups are protected; are usedto prepare compounds of formula i(e). These compounds are well known inthe art and to the extent not commercially available, are readilysynthesized by standard procedures commonly employed in the art.

Compounds of formula i(b) where Y is —E—NR²R³ and A, E, R², and R³ areas described supra and Pg is an amino protecting group can be preparedby reductive animation as illustrated in Scheme 3 from compounds offormula i(a) wherein Y is —E—C(O)R¹ and R¹ is hydrogen.

Compounds of formula i(b) may be prepared from compounds of formula i(a)in a manner similar to that as taught in the Larock, “ComprehensiveOrganic Transformations”, pg. 421-430, VCH Publishers, New York, N.Y.,1989, hereafter referred to as “Larlock”.

Additionally, the skilled artisan will appreciate that the compounds offormula i(b) may also be prepared from compounds of i(c) as is shown inScheme 4.

Compounds of formula i(b) may be prepared by reductive alkylation fromcompounds of formula i(c) in a manner similar to that as taught in theLarock reference at pages 434-435. Compounds of formulas i(a) and i(c)are well known in the art and to the extent not commercially available,are readily synthesized by standard procedures commonly employed in theart.

Compounds of formula i(d) where Y is C(O)R¹ and R¹ is NR²R⁴ may beprepared from compounds of formula i(e) as illustrated in Scheme 5 belowwhere E, A, and Pg are as described supra.

Compounds of formula i(e) may be converted to other compounds of theinvention via solution or solid phase synthetic techniques. For example,acids of formula i(e) may be ted with activating agents to form theactivated carboxylic acid derivatives of formula i(e) by methods wellknown in the chemical arts. See, e.g., The Peptides, Peptide Synthesisand the Examples and Preparations sections below.

Generally, preparation of compounds of formula i(d) where R¹ is NR²R⁴ isperformed in a manner similar to that as taught in the Larock referenceat pages 972-976. Specifically, such compounds of formula i(d) may beprepared by dissolving or suspending a compound of the activatedcarboxylic acid derivatives of formula i(e) in a suitable solvent,optionally in the presence of a suitable base, and adding an amine offormula III. Typically a preferred and convenient solvent isdichloromethane. Preferred bases are triethylamine andpiperidinylmethylpolystyrene resin. The amine is typically employed inmolar excess. For example, about a 1.5 to about a 3 molar excess,relative to the compound of the activated carboxylic acid derivatives offormula i(e) is usually employed. About 1.8 to about 2.2 fold molarexcess is typically preferred. The reaction is usually performed in atemperature range of about 0° C. to about the reflux temperature of thesolvent for from 10 minutes to 18 hours. Preferably, the reaction isperformed at about 15° C. to about 40° C. for from 5 minutes to about2.5 hours.

Furthermore, the transformations described in Schemes 2-5 may beperformed after the cyclization described in Scheme 1 to provide thecompounds of formula I with a fully elaborated R substituent.

Scheme 6 describes generically the tricyclic salt formation of5H-isoxazolo[4,5-c]quinolin-4-one from the carboxylic acid compounds,represented by the compound of formula XI(a). Compounds of formula XI(a)are commercially available and may be prepared by common synthetictechniques, see e.g. WO99/51227.

Additionally, compounds of formula XI(a) may be prepared in a mannersimilar to that described in the literature, for example, see Chen Y P,et. al, Heterocycles, 1995, 41, 175, and Chantegrel B, et. al, J. Org.Chem, 1984, 49, 4419-4424.

Compounds of formula XI(a) may be converted to the tricyclic salt usedin the palladium chemistry method described supra, by converting thecompound of formula XI(a) to the corresponding carboxamide, thencyclizing the piperidine ring as generally described in Scheme 1.

The pharmaceutical salts of the invention are typically formed byreacting a compound of formula I with an equimolar or excess amount ofacid or base. The reactants are generally combined in a mutual solventsuch as diethylether, tetrahydrofuran, methanol, ethanol, isopropanol,benzene, and the like for acid addition salts, or water, an alcohol or achlorinated solvent such as dichloromethane for base addition salts. Thesalts normally precipitate out of solution within about one hour toabout ten days and can be isolated by filtration or other conventionalmethods.

Acids commonly employed to form pharmaceutical acid addition salts areinorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodicacid, sulfuric acid, phosphoric acid, and the like, and organic acidssuch as p-toluenesulfonic, methanesulfonic acid, ethanesulfonic acid,oxalic acid, p-bromophenylsulfonic acid, carbonic acid, succinic acid,citric acid, tartaric acid, benzoic acid, acetic acid, and the like.Preferred pharmaceutical acid addition salts are those formed withmineral acids such as hydrochloric acid, hydrobromic acid, and sulfuricacid, and those formed with organic acids such as maleic acid, tartaricacid, and methanesulfonic acid.

Bases commonly employed to form pharmaceutical base addition salts areinorganic bases, such as ammonium or alkali or alkaline earth metalhydroxides, carbonates, bicarbonates, and the like. Such bases useful inpreparing the salts of this invention thus include sodium hydroxide,potassium hydroxide, ammonium hydroxide, potassium carbonate, sodiumcarbonate, sodium bicarbonate, potassium bicarbonate, calcium hydroxide,calcium carbonate, and the like. The potassium and sodium salt forms areparticularly preferred.

It should be recognized that the particular counterion forming a part ofany salt of this invention is not of a critical nature, so long as thesalt as a whole is pharmacologically acceptable and as long as thecounterion does not contribute undesired qualities to the salt as awhole.

The optimal time for performing the reactions of Schemes 1-6 can bedetermined by monitoring the progress of the reaction via conventionalchromatographic techniques. Furthermore, it is preferred to conduct thereactions of the invention under an inert atmosphere, such as, forexample, argon, or, particularly, nitrogen. Choice of solvent isgenerally not critical so long as the solvent employed is inert to theongoing reaction and sufficiently solubilizes the reactants to effectthe desired reaction. The compounds are preferably isolated and purifiedbefore their use in subsequent reactions. Some compounds may crystallizeout of the reaction solution during their formation and then collectedby filtration, or the reaction solvent may be removed by extraction,evaporation, or decantation. The intermediates and final products offormula I may be further purified, if desired by common techniques suchas recrystallization or chromatography over solid supports such assilica gel or alumina.

The skilled artisan will appreciate that not all substituents arecompatible with all reaction conditions. These compounds may beprotected or modified at a convenient point in the synthesis by methodswell known in the art. For example, the skilled artisan would appreciatethat when A is in the diol or acetonide form, the conversion from thecyclopentenyl to these forms would be done in the last step.

The following Preparations and Examples are provided to better elucidatethe practice of the present invention and should not be interpreted inany way as to limit the scope of same. Those skilled in the art willrecognize that various modifications may be made while not departingfrom the spirit and scope of the invention. All publications mentionedin the specification are indicative of the level of those skilled in theart to which this invention pertains. The terms and abbreviations usedin the instant Preparations and Examples have their normal meaningsunless otherwise designated. For example “° C.”, “N”, “mmol”, “g”, “mL”,“M”, “HPLC”, “IR”, “MS(FD)”, “MS(IS)”, “MS(FIA)”, “MS(FAB)”, “MS(EI)”,“UV”, and “¹H NMR”, refer to degrees Celsius, normal or normality,millimole or milimoles, gram or grams, milliliter or milliliters, molaror molarity, high performance liquid chromatography, infra redspectrometry, field desorption mass spectrometry, ion spray massspectrometry, flow injection analysis mass spectrometry, fast atombombardment mass spectrometry, electron impact mass spectrometry,ultraviolet spectrometry, and proton nuclear magnetic resonancespectrometry respectively. In addition, the absorption maxima listed forthe IR spectra are only those of interest and not all of the maximaobserved.

PREPARATIONS Preparation 1

9-Chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one Potassium Salt

To 3-(6-chloro-2-fluorophenyl)-5-methyhsoxazol-4-carboxamide (2.51 g,9.86 mmol) in 25 mL anhydrous DMF at −20° C. was added 0.5 M KHMDS intoluene (23.7 mL, 11.8 mmol). After 20 minutes the cold bath was removedand the mixture was stirred for an additional 40 minutes. A yellowprecipitate formed. After filtration 1.78 g (66%) of the title compoundwere obtained.

Preparation 2

4-(t-Butyldimethylsilanyloxy)cyclopent-2-enyloxy Acetate

To a stirred solution of 4-hydroxy-cyclopent-2-enyloxy acetate (4.1 g,29 mmol) in CH₂Cl₂ (35 mL) and 2,6-lutidine (8.2 mL, 67 mmol) was addedt-butyldimethylsilyl trifluoromethanesulfonate (10 mL, 44 mmol) at 0-5°C. The reaction mixture was stirred at r.t. for 1 hour. It was dilutedwith CH₂Cl₂, washed (brine), dried (Na₂SO₄), filtered and concentratedColumn chromatography (silica gel, 5:1 hexanes:diethylether) gavedesired product (5.1 g, 69%). ¹H NMR (CDCl₃, 400 MHz) δ; 5.88 (m, 1H);5.84 (m, 1H); 5.42 (t, 1H); 4.64 (t, 1H); 2.80 (m, 1H); 2.02 (s, 3H);1.59 (m, 1H); 0.83 (s, 9H); 0.04 (s, 6H).

Preparation 3

5-[4-(t-Butyldimethylsilanyloxy)cyclopent-2-en-1-yl]-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one

To a stirred solution of4-(t-butyldimethylsilanyloxy)cyclopent-2-enyloxy acetate (3.4 g, 13.3mmol) in DMF (140 mL) was added tetrakis(triphenylphosphine)palladium(1.54 g, 1.3 mmol) and9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one potassium salt (4.4g, 16.2 mmol). The reaction mixture was stirred at 55° C. for 6 hours.It was diluted with ethyl acetate, washed (brine), dried (Na₂SO₄),filtered and concentrated. Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave desired product (5.7 g, 67%). ¹HNMR (CDCl₃, 400 MHz) δ; 7.83 (m, 1H); 7.22 (m, 2H); 6.50 (t, 1H); 5.84(m, 2H); 4.85 (t, 1H); 2.82 (s, 3H); 2.78 (m, 1H); 2.02 (m, 1H); 0.81(s, 9H); 0.02 (s, 3H); 0.00 (s, 3H).

Preparation 4

9-Chloro-5-(4-hydroxy-cyclopent-2-enyl]-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one

To a stirred solution of5-[4-(t-butyl-dimethylsilanyl-oxy)cyclopent-2-en-1-yl]-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(3.4 g, 7.9 mmol) in THF (60 mL) was added HF pyridine/pyridine/THF(1:2:8; 50 mL). The mixture was stirred at r.t. for 6 hours. SolidNaHCO₃ (6 g) and ethyl acetate (60 mL) were added. Aqueous NaHCO₃ wasthen added until the reaction was quenched The layers were separated andthe organic fraction was washed (brine, water, aqueous CuSO₄), dried(Na₂SO₄), filtered and concentrated. Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave desired product (2.2 g, 88%). ¹HNMR (CDCl₃, 400 MHz) δ; 7.59 (d, 1H); 7.37 (t, 1H); 7.30 (d, 1H); 6.15(m, 1H); 5.91 (m, 1H); 5.78 (broad, 1H); 4.82 (broad, 1H); 2.81 (s, 3H);2.82 (m, 1H); 2.18 (m, 1H).

Preparation 5

Carbonic Acid4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl-cyclopent-2-enylEster Ethyl Ester

To a stirred solution of9-chloro-5-(4-hydroxy-cyclopent-2-enyl]-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(430 mg, 1.37 mmol) in CH₂Cl₂ (10 mL) was added pyridine (0.55 mg, 6.85mmol) and ethyl chloroformate (0.16 mL, 1.64 mmol) and sired at r.t. for5.5 hour. The mixture was diluted with CH₂Cl₂, washed (brine), dried(Na₂SO₄), filtered and concentrated. Column chromatography (silica gel,5:1 hexanes/ethyl acetate) gave desired product (0.47 g, 89%). ¹H NMR(CDCl₃, 400 MHz) δ; 7.62 (d, 1H); 7.37 (t, 1H); 7.34 (d, 1H); 6.52 (t,1H); 6.20 (m, 1H); 6.09 (m, 1H); 5.73 (t, 1H); 4.19 (q, 2H); 2.98 (m,1H); 2.88 (s, 3H); 2.28 (m, 1H); 1.26 (t, 3H).

Preparation 6

5-(4-Aminocyclopent-2-enyl)9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one

To a stirred solution of carbonic acid4-(9-chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl-cyclopent-2-enylester ethyl ester (2 g, 5.1 mmol) in THF (30 mL) was addedtetrakis(triphenylphosphine) palladium (1.2 g, 1.0 mmol) and a solutionof potassium di-t-butyl iminodicarboxylate in THF (75 mL, 0.2 M, 15mmol). The reaction mixture was stirred at 55° C. for 6 hours. It wasthen diluted with ethyl acetate, washed (brine), dried (Na₂SO₄),filtered and concentrated. Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave a mixture of the coupling productand di-tert-butyl iminodicarboxylate, which was treated withtrifluoroacetic acid (5 mL). The mixture was stirred 6 hours at roomtemperature. It was then concentrated, dissolved in water, treated withNaOH solution (5N), extracted with EtOAc, dried over Na₂SO₄,concentrated, and gave the desired product (0.62 g, 39%). ¹H NMR (CDCl₃,400 MHz) δ; 7.72 (d, 1H); 7.35 (t, 1H); 7.26 (d, 1H); 6.19 (t, 1H); 5.90(m, 2H); 4.10 (m, 1H); 2.88 (s, 3H); 2.80 (m, 1H); 1.90 (m, 1H).

Preparation 7

N-[4-(Hydroxymethyl)cyclopent-2-enyl](t-butoxy)carboxamide

4-t-Butoxycarbonylaminocyclopent-2-enecarboxylic acid (1 g, 4.4 mmol)was dissolved in THF (10 mL) and borane-THF (1.5 mL, 1M solution) wasadded drop-wise at 0° C. and stirred overnight at rt. The reactionmixture was poured into ice-cold water (10 mL) and extracted with ethylacetate (2×50 mL). The ethyl acetate extract was washed with brine,dried over sodium sulfate, filtered and evaporated to yieldN-[4-(hydroxy-methyl)cyclopent-2-enyl](t-butoxy)carboxamide (655 mg,69%). ESMS: 214 (M+1)⁺, 236 (M+23)⁺, 248 (M+35)⁻, 272 (M+59)⁻. ¹H NMR(CDCl₃): δ 1.40 (s, 9H), 2.16 (s, 1H), 2.44-2.52 (m, 2H), 2.82-2.83 (m,1H), 3.54-3.66 (m, 2H), 5.74-5.81 (m, 2H).

Preparation 8

(1S,4R)-4-(9-Chloro-3-methyl-4-oxo(5-hydroisoxazolo[4,3-c]quinolin-5-yl))cyclopent-2-enylAcetate

A solution of N-[4-(hydroxymethyl)cyclopent-2-enyl](t-butoxy)carboxamide(1.58 g, 5.00 mmol), pyridine (1.21 ml, 15.0 mmol), acetic anhydride(0.94 ml, 10.0 mmol) in CH₂Cl₂ (20 ml) was stirred for 17 h. The mixturewas diluted with CH₂Cl₂, extracted with 1N HCl, H₂O, and brine, anddried (MgSO₄). Column chromatography (silica gel, hexanes:EtOAcgradient) gave the title compound (1.63 g, 91%). ¹H NMR (CDCl₃, 400 MHz)δ 7.64 (dd, 1H, J=1.5, 7.8 Hz), 7.36-7.29 (m, 2H), 6.46 (br S, 1H), 6.16(m, 1H), 6.04 (m, 1H), 5.77 (m, 1H), 2.97 (ddd, 8.3, 8.8, 14.2 Hz), 2.89(s, 3H), 2.18 (ddd, 1H, J=7.3, 7.3, 12.2 Hz), 2.08 (s, 3H) ppm.

Preparation 9

Dimethyl2-[(1S,4R)-4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo-[4,3-c]quinolin-5-yl)cyclopent-2-enyl]propane-1,3-dioate

To a solution of(1S,4R)-4-(9chloro-3-methyl-4-oxo(5-hydroisoxazolo[4,3-c]quinolin-5-yl))cyclopent-2-enylacetate (1.55 g, 4.33 mmol) in THF (N₂) was added Pd(PPh₃)₄ (500 mg,0.43 mmol) under a positive flow of N₂ followed by a solution of sodiumdimethyl malonate (43.3 ml at 0.2 M in THF, 8.66 mmol). The mixture washeated to 50-55° C. for 6 h then cooled to room temperature. Dilutionwith EtOAc, extraction with H₂O and brine, drying (MgSO₄), and columnchromatography (silica gel, hexanes:ethyl acetate gradient) gave thetitle compound (1.38 g, 74%). ¹H NMR (CDCl₃, 400 MHz) δ 7.70 (d, 1H,J=8.3 Hz), 7.35 (t, 1H, J=8.1 Hz), 7.29 (d, 1H, J=7.8 Hz), 6.35 (br s,1H), 5.98 (m, 1H), 5.90 (m, 1H), 3.75 (s, 3H), 3.73 (m, 1H), 3.70 (s,3H), 3.60 (d, 1H, J=8.8 Hz), 3.50 (m, 1H), 2.87 (s, 3H), 2.60 (ddd, 1H,J=8.3, 8.3, 12.7 Hz), 2.03 (ddd, J=9.3, 9.3, 13.2 Hz) ppm.

Preparation 10

Methyl2-[(1R,4R)-4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl))cyclopent-2-enyl]acetate

A solution of dimethyl2-[(1S,4R)-4-(9-chloro-3-methyl-4-oxo-5H-isoxazolo-[4,3-c]quinolin-5-yl)cyclopent-2-enyl]propane-1,3-dioate(1.00 g, 2.33 mmol), LiCl (0.200 g, 4.66 mmol), and H₂O (0.084 ml, 4.7mmol) in DMSO (15 ml) was lowered into an oil bath at 180° C. andstirred for 4 h. The reaction was cooled to room temperature, dilutedwith EtOAc (50 ml), extracted with H₂O and brine, dried (MgSO₄), andchromatographed (silica gel, hexanes:EtOAc gradient) to give the titlecompound (450 mg, 52%). Mass spectrum (ES+) (m/z) 373.0 [M+1].

Preparation 11

N-[4-(Toluene-4-sulfonoxymethyl)cyclopent-2-enyl](t-butoxy)carboxamide

N-[4-(Hydroxymethyl)cyclopent-2-enyl](t-butoxy)carboxamide (655 mg, 3mmol) was dissolved in methylene chloride (20 mL) and p-toluenesulfonylchloride (131 mg, 0.69 mmol), triethyl amine (268 μL, 1.86 mmol) andDMAP (10 mg) were added and stirred overnight. The methylene chloridesolution was washed with 1M HCl (2×10 mL), water (2×10 mL), brine (2×10mL), dried over sodium sulfate, filtered and evaporated to yieldN-[4-(Toluene-4-sulfonoxymethyl)cyclopent-2-enyl](t-butoxy)carboxamide(1.0g, 90%).

ESMS: 368 (M+1)⁺, 426 (M+59)⁻. ¹H NMR (CDCl₃): δ 1.40 (s, 9H), 2.05 (s,1H), 2.44 (s, 3H), 2.44-2.50 (m, 2H), 2.89 (br s, 1H), 3.91-3.96 (m,2H), 4.10-4.15 (m, 1H), 5.77 (2d, 2H), 7.33-7.35 (d, 2H), 7.75-7.78 (d,2H).

Preparation 12

N-[4-(Azidomethyl)cyclopent-2-enyl](t-butoxy)carboxamide

To a solution ofN-[4-(toluene-4-sulfonoxymethyl)-cyclopent-2-enyl](t-butoxy)carboxamide(1 g, 2.7 mmol) dissolved in DMF (10 mL) sodium azide was added andstirred at 80° C. overnight. The reaction mixture was diluted with ethylacetate (50 mL) and washed with water (2×25 mL), brine (2×25 mL), driedover sodium sulfate, filtered and evaporated to yieldN-[4-(azidomethyl)cyclopent-2-enyl](t-butoxy)carboxamide. IR(chloroform): ν 2096.6 cm⁻¹ (azide). ¹H NMR (CDCl₃): δ 1.27-1.30 (m,2H), 1.43 (s, 9H), 2.51-2.56 (m, 2H), 3.27-3.35 (m, 2H), 5.76 (s, 2H).

Preparation 13

4-Azidomethyl-cyclopent-2-enylamine

N-[4-(azidomethyl)cyclopent-2-enyl](t-butoxy)-carboxamide (10 g, 42mmol) was dissolved in TFA reagent (9.25 mL TFA, 0.25 mL anisole, 0.25mL triisopropylsilane and 0.25 mL water)and DCM (25 mL), and stirred for30 min at rt. The reaction mixture was concentrated and the residuefiltered through SCX column, eluted with ammonia (2 M solution inmethanol), and evaporated to yield the title compound (4.6 g, 80%).:ESMS: 139 (M+1)⁺. ¹H NMR (CDCl₃): δ 1.40-1.55 (m, 1H), 2.45-2.60 (m,1H), 2.90-3.00 (m, 1H), 3.40 (d, 2H), 4.104.20 (m, 1H), 5.90 (s, 2H).

Preparation 14

N-[4-(Azidomethyl)cyclopent-2-enyl][5-methyl-3-(6-chloro-2-fluorophenyl)isoxazol-4-yl]carboxamide

A mixture of 4-azidomethyl-cyclopent-2-enylamine (4.6 g, 33 mmol),2-chloro-6-fluorophenylisoxazoyl chloride (13.5 g, 49 mmol), triethylamine (5 mL) and DMAP (100 mg) dissolved in DCM (200 mL) was stirredovernight at r.t The reaction mixture was washed with HCl (1M, 2×10 mL),water (2×10 mL), brine (2×10 mL), dried over sodium sulfate, filtered,and evaporated to yieldN-[4-(azidomethyl)cyclopent-2-enyl][5-methyl-3-(6-chloro-2-fluorophenyl)isoxazol-4-yl]carboxamide(10 g, crude, 83%). ESMS: 376 (M+1)⁺. ¹H NMR (CDCl₃): δ 2.40-2,70 (m,2H), 2.80 (d, 2H), 2.80-3.50 (m, 2H), 500 (brs, 1H), 5.40-5.90 (m, 2H),7.05-7.50 (m, 3H).

EXAMPLES Example 1

N-{4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)cyclopent-2-enyl}benzamide

To a sired solution of5-(4-amino-cyclopent-2-enyl)9-chloro-3-methyl-5H-isoxazolo[4,3c]quinolin-4-one(28.7 mg, 0.091 mmol) in CH₂Cl₂ (2 mL) was added benzoyl chloride (0.013mL, 0.11 mmol) and triethyl amine (0.1 mL) and stirred at r.t. for 6hours. The mixture was diluted with CH₂Cl₂, washed (brine), dried(Na₂SO₄), filtered and concentrated. Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave title compound (21 mg, 55%). MassSpectrum (FIA) (m/z) 420.2 (M+1). ¹H NMR (CDCl₃): δ 7.83 (d, 2);7.38-7.61 (m, 6H); 6.08 (m, 1H); 5.96 (m, 1H); 5.58 (s, 1H); 5.40 (t,1H); 3.02 (m, 2H); 2.18 (m, 2H).

Example 2

1-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-enyl]3-phenyl-urea

To a stirred solution of5-(4amino-cyclopent-2-enyl)9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(50 mg, 0.16 mmol) in CH₂Cl₂ (2 mL) was added isocyanatobenzene (0.018mL, 0.18 mmol) and DMAP (catalytic amount) and stirred at r.t for 2hours. The mixture was diluted with CH₂Cl₂, washed (brine), dried(Na₂SO₄), filtered and concentrated Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave the tide compound (35 mg, 50%).Mass Spectrum (M) (m/z) 433.3 (M−1). Anal. Calc. For C₂₃H₁₉ClN₄O₃;Theoretical: C, 63.52, H, 4.40, N, 12.88%; Found: C, 63.82, H, 4.45, N,12.49%.

Example 3

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4.3-c]quinolin-5-yl)-cyclopent-2-enyl]2-oxo-2-(3,4,5-trimethoxy-phenyl)-acetamide

To a stirred solution of5-(4-amino-cyclopent-2-enyl)-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(50 mg, 0.216 mmol) in CH₂Cl₂ (2 mL) was addedoxo-(3,4,5-trimethoxy-phenyl)acetyl chloride (80 mg, 0.33 mmol, preparedfrom its acid and oxalyl chloride) and DMAP (catalytic amount) andstirred at r.t. for 18 hours. The mixture was diluted with CH₂Cl₂,washed (brine), dried (Na₂SO₄), filtered and concentrated. Columnchromatography (silica gel, hexanes/ethyl acetate, gradient) gave thetitle compound (33 mg, 38%). Mass Spectrum (FIA) (m/z) 538A 4 (A+1). ₁HNMR (CDCl₃): δ 7.80 (d, 1H); 7.50 (t, 1H); 7.35 (d, 1H); 6.00 (m, 2H);5.40 (m, 1H); 5.21 (m, 111); 3.80-3.90 (m, 1H); 2.95 (s, 3H); 2.30 (m,1H).

Example 4

1-[4(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)cyclopent-2-enyl]3-(3,4,5-trimethoxy-phenyl)-urea

To a stirred solution of5-(4amino-cyclopent-2-enyl)9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(69 mg, 0.22 mmol) in CH₂Cl₂ (5 mL) was added3,4,5-trimethoxy-isocyanato benzene (55 mg, 0.26 mmol) and DMAP(catalytic amount) and stirred at rt. for 18 hours. The mixture wasdiluted with CH₂Cl₂, washed (brine), dried Na₂SO₄), filtered andconcentrated. Column chromatography (silica gel, hexanes/ethyl acetate,gradient) gave the title compound (116 mg, 100%). Mass Spectrum (FIA)(m/z) 425.3 (M+1) ¹H NMR (CDCl₃): δ 7.45 (d, 1H); 7.40 (t, 1H); 7.33 (d,1H); 6.58 (m, 3H); 5.95 (m, 1H); 5.83 (m, 1H); 5.18 (s, 1H); 3.78 (s,9H); 2.98 (m, 2H); 2.05 (m, 2H).

Example 5

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-enyl]2-phenyl)acetamide

To a stirred solution of5-(4-amino-cyclopent-2-enyl)-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(47.6 mg, 0.15 mmol) in CH₂Cl₂ (2 mL) was added phenyl acetic acid (27mg, 0.20 mmol), Et₃N (0.052 mL, 0.38 mmol) and EDCI (38 mg, 0.20 mmol)and stirred at r.t. for 18 hours. The mixture was diluted with CH₂Cl₂,washed (brine), dried (Na₂SO₄), filtered and concentrated Columnchromatography (silica gel, hexanes/ethyl acetate, gradient) gave thetitle compound (36 mg, 56%). Mass Spectrum (FIA) (m/z) 434.4 (M+1).Anal. Calc. For C₂₄H₂₀ClN₃O₃. Theoretical: C, 66.44, H, 4.65, N, 9.68%.Found. C, 66.18, H, 4.71, N, 9.32%.

Example 6

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-enyl]2-(2-methoxy-phenyl)-acetamide

To a stirred solution of5-(4-amino-cyclopent-2-enyl)-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(97 mg, 0.31 mmol) in CH₂Cl₂ (4 mL) was added 2-methoxy phenyl aceticacid (66.3 mg, 0.40 mmol), Et₃N (0.11 ml, 0.40 mmol) and EDCI (77 mg,0.40 mmol) and stirred at r.t. for 18 hours. The mixture was dilutedwith CH₂Cl₂, washed (brine), dried (Na₂SO₄), filtered and concentrated.Column chromatography (silica gel, hexanes/ethyl acetate, gradient) gavethe title compound (59 mg, 41%). Mass Spectrum (FIA) (m/z) 464.2 (M+1)Anal. Calc. For C₂₅H₂₂ClN₃O₄. Theoretical: C, 64.73, H, 4.78, N, 9.06%.Found. C, 64.78, H, 4.91, N, 8.83%.

Example 7

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-enyl]2-(3,4,5-trimethoxy-phenyl)-acetamide

To a stirred solution of5-(4-amino-cyclopent-2-enyl)-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(47 mg, 0.15 mmol) in CH₂Cl₂ (2.5 mL) was added 3,4,5-trimethoxy phenylacetic acid (45 mg, 0.20 mmol), Et₃N (0.053 mL, 0.38 mmol) and EDCI (38mg, 0.20 mmol) and stirred at r.t. for 18 hours. The mixture was dilutedwith CH₂Cl₂, washed (brine), dried (Na₂SO₄), filtered and concentrated.Column chromatography (silica gel, hexanes/ethyl acetate, gradient) gavethe title compound (23 mg, 29%). Mass Spectrum (FIA) (m/z) 522.2 (M−1).¹H NMR (CDCl₃): δ 7.43 (d, 1H); 7.37 (m, 2H); 6.42 (s, 2H); 5.88 (m,2H); 5.18 (m, 1H); 3.78 (s, 9H); 3.47 (s, 2H); 2.90 (m, 2H); 1.98 (m,2H).

Example 8

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-emyl]2-(3-fluoro-phenyl)-acetamide

To a stirred solution of5-(4-amino-cyclopent-2-enyl)-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(16 mg, 0.05 mmol) in CH₂Cl₂ (3 mL) was added 3-fluoro phenyl aceticacid (1.9 mg, 0.01 mmol), Et₃N (0.003 mL, 0.03 mmol) and EDCI (2.4 mg,0.01 mmol) and stirred at r.t for 18 hours. The mixture was diluted withCH₂Cl₂, washed (brine), dried (Na₂SO₄), filtered and concentrated.Column chromatography (silica gel, hexanes/ethyl acetate, gradient) gavethe title compound (17 mg, 74%). Mass Spectrum (FIA) (m/z) 452.0 (M+1).¹H NMR (CDCl₃): δ 7.25-7.42 (m, 4H); 7.00 (m, 3H); 5.82 (m, 2H); 5.20(t, 1H); 3.58 (s, 2H); 2.90 (m, 21); 1.89 (m, 2H).

Example 9

{[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-enylcarbamoyl]-phenyl-methyl}-carbamicacid t-butyl ester

To a stirred solution of5-(4-amino-cyclopent-2-enyl)-9-chloro-3-methyl-5H-isoxazolo[4,3-c]quinolin-4-one(38 mg, 0.12 mmol) in CH₂Cl₂ (2.5 mL) was added D-boc-phenyl glycine (39mg, 0.16 mmol), Et₃N (0.033 mL, 0.24 mmol), DMAP (catalytic amount),HOBT (16 mg, 0.12 mmol) and EDCI (31 mg, 0.16 mmol) and stirred at r.t.for 18 hours. The mixture was diluted with CH₂Cl₂, washed (brine), dried(Na₂SO₄), filtered and concentrated. Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave the title compound (56 mg, 85%).Mass Spectrum (FD) (m/z) 549 (M⁺). ¹H NMR (CDCl₃): δ 7.48 (m, 8H); 5.59(m, 1H); 5.57 (m, 1H); 5.52 (s, 1H); 5.10 (m, 2H); 2.85 (s, 3H); 2.05(tt, 1H); 1.49 (s, 9H).

Example 10

{[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-enylcarbamoyl]-phenyl-methyl)-carbamicacid t-butyl ester

To a stirred solution of5-(4-amino-cyclopent-2-enyl)-9-chloro-3-methyl-5H-isoxazolo[4,3c]quinolin-4-one(38 mg, 0.12 mmol) in CH₂Cl₂ (2.5 mL) was added L-boc-phenyl glycine (39mg, 0.16 mmol), Et₃N (0.033 mL, 0.24 mmol), DMAP (catalytic amount),HOBT (16 mg, 0.12 mmol) and EDCI (31 mg, 0.16 mmol) and stirred at r.t.for 18 hours. The mixture was diluted with CH₂Cl₂, washed (brine), dried(Na₂SO₄), filtered and concentrated. Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave the title compound (53 mg, 81%).Mass Spectrum (FIA) (m/z) 449 (M-Boc). ¹H NMR (CDCl₃): δ 7.75-7.4 (m,8H); 5.90-6.00 (m, 2H); 5.51 (s, 1H); 5.53 (m, 2H); 2.75 (m, 4H); 1.91(tt, 1H); 1.49 (s, 9H).

Example 11

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-2,3-dihydroxycyclopentyl]-2-(3,4,5-trimethoxy-phenyl)-acetamide

To a stirred solution ofN-[4-(9-chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-cyclopent-2-enyl]2-(3-fluorophenyl)-acetamide(54 mg, 0.10 mmol) in acetone (8 mL) and THF (3 mL) was added NMO (43mg, 0.32 mmol, 50% aqueous solution) and OsO₄ (catalytic amount) andstirred at r.t. for 5 hours. The mixture was diluted with EtOAc,quenched with aqueous Na₂S₂O₈ and separated. The organic layer waswashed (brine), dried (Na₂SO₄), filtered and concentrated. Columnchromatography (silica gel, hexanes/ethyl acetate, gradient) gave thetitle compound (29 mg, 52%). Mass Spectrum (FIA) (m/z) 558.2 (M+1) ₁ ¹HNMR (CDCl₃): δ 7.51 (d, 1H); 7.40 (t, 1H); 7.32 (d, 1H); 6.91 (d, 1H);6.43 (s, 2H); 4.80 (m, 1H); 4.72 (t, 1H); 4.30 (m, 1H); 4.24 (t, 1H);3.80 (s, 6H); 3.78 (s, 3H); 3.52 (s, 2H); 2.80 (s, 3H); 2.49 (m, 1H);2.08 (m, 1H).

Example 12

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)2,3-dmethyltetrahydro-cyclopenta[1,3]dioxol-4-yl]-2-(3,4,5-trimethoxy-phenyl)-acetamide

To a stirs solution ofN-[4-(9-chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)2,3-dihydroxy-cyclopentyl]-2-(3,4,5-trimethoxy-phenyl)-acetamide(114 mg, 0.20 mmol) in CH₂Cl₂ (1 mL) was added 2,2-dimethoxy propane(0.25 mL, 2 mmol) and PPTS (25 mg, 1 mmol) and stirred at r.t for 18hours. The mixture was diluted with CH₂Cl₂, washed (brine), dried(Na₂SO₄), filtered and concentrated. Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave the title compound (83 mg, 69%).Mass Spectrum (FIA) (m/z) 598.2 (M+1) Anal. Calc. For C₃₀H₃₂ClN₃O₈.Theoretical: C, 60.25, H, 5.39, N, 7.03%. Found. C, 60.42, H, 5.51, N,7.14%.

Example 13

N-[4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-2,3-dihydroxycyclopentyl]-2-(3-fluoro-phenyl)-acetamide

To a stirred solution ofN-[3-(9-chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)cyclopentonyl-2(3-fluoro-phenyl-methyl}-acetamide(182 mg, 0.40 mmol) in acetone (5 mL) and THF (20 mL) was added NMO (173mg, 1.30 mmol, 50% aqueous solution) and OsO₄ (catalytic amount) andstirred at r.t 72 hours. The mixture was diluted with EtOAc, quenchedwith aqueous Na₂S₂O₈ and separated. The organic layer was washed(brine), dried (Na₂SO₄), filtered and concentrated. Columnchromatography (silica gel, hexanes/ethyl acetate, gradient) gave thetitle compound (170 mg, 88%).

Mass Spectrum (FIA) (m/z) 486.1 (M+1). ¹H NMR (CDCl₃): δ 7.55 (d, 1H);7.42 (t, 2H); 7.33 (d, 1H); 7.23 (d, 1H); 7.02 (dd, 1H); 6.93 (t, 1H);6.81 (d, 1H); 4.80 (m, 1H); 4.70 (s, 1H); 4.25 (n, 2H); 4.10 (s, 1H);3.60 (s, 2H); 2.92 (s, 3H); 2.50 (m, 1H); 2.08 (m, 1H).

Example 14

N-[6-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)2,3-dimethyltetahydro-cyclopenta[1,3]dioxol-4-yl]-2-(3-fluoro-phenyl)-acetamide

To a stirred solution ofN-[4-(9-chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)-2,3-dihydroxy-cyclopentyl]-2-(3-fluorophenyl)-acetamide(69 mg, 0.14 mmol) in CH₂Cl₂ (1 mL) was added 2,2-dimethoxy propane(0.18 mL, 1.42 mmol) and PPTS (18 mg, 0.07 mmol) and stirred at r.t for18 hours. The mixture was diluted with CH₂Cl₂, washed (brine), dried(Na₂SO₄), filtered and concentrated Column chromatography (silica gel,hexanes/ethyl acetate, gradient) gave the title compound (50 mg, 65%).

Mass Spectrum (FIA) (m/z) 548.1 (M+Na). ¹H NMR (CDCl₃): δ 7.43 (t, 2H);7.37 (d, 1H); 7.31 (d, 1H); 7.11 (tt, 1H); 6.80-6.96 (m, 3H); 5.04 (d,1H); 4.71 (m, 2H); 4.62 (m, 1H); 3.43 (s, 2H); 2.95 (m, 1H); 2.80 (s,3H); 1.81 (tt, 1H); 1.55 (s, 3H); 1.48 (s, 3H).

Example 15

2-[(1R,4R)-4-(9-Chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl)cyclopent-2-enyl]-N-(3,4,5-trimethoxyphenyl)acetamide

A solution of methyl2-[(1R,4R)-4-(9-chloro-3-methyl-4-oxo-5H-isoxazolo[4,3-c]quinolin-5-yl))cyclopent-2-enyl]acetate(0.200 g, 0.54 mmol) and NaOH (2 ml at 2 N, 4.00 mmol) in dioxane (5ml)was heated to 59° C. for 2 h. Upon cooling to room temperature thevolatiles were removed under reduced pressure. The residue was dissolvedup in H₂O (10 ml), acidified with 1 N HCl until a pH of 2 and extractedwith EtOAc. The organic fractions were washed H₂O and brine) and driedMgSO₄) to give the crude acid after removal of the solvent. The crudeacid, 3,4,5-trimethoxyaniline (148 mg, 0.81 mmol), and EDCI (210 mg,1.10 mmol)were dissolved in CH₂Cl₂ (5 ml) followed by the addition ofDMAP (6 mg , 0.05 mmol). The mixture was e for 18 h. Dilution withCH₂Cl₂ followed by direct application of the mixture to a silica gelcolumn and elution (hexanes:EtOAc) gave the title compound (173 mg,61%). Mass spectrum (ES−) (m/z) 522.3 [M−1].

The compounds of the invention are inhibitors of MRP1. Thus, thecompounds of the invention may be used to inhibit any neoplasm havingintrinsic and/or acquired resistance, conferred in part or in total byMRP1, to an oncolytic or oncolytics. In other words, treatment of such aneoplasm with an effective a mount of a compound of this invention willcause the neoplasm to be more sensitive to chemotherapy that waspreviously rendered less efficacious by MRP1.

Vincristine, epirubicin, daunorubicin, doxorubicin, and etoposide areoncolytics that are substrates of MRP1. See Cole, et. al.,“Pharmacological Characterization of Multidrug Resistant MRP-transfectedHuman Tumor Cells”, Cancer Research, 54:5902-5910, 1994. Since MRP1 isubiquitous in mammals, particularly humans, Nooter, K, et. al.,“Expression of the Multidrug Resistance-Associated Protein (MRP) Gene inHuman Cancers”, Clin. Can. Res., 1:1301-1310, (1995), chemotherapy whosegoal is to inhibit a neoplasm employing any of those agents has thepotential to be rendered less efficacious by MRP1. Thus, neoplasms ofthe bladder, bone, breast, lung(small-cell), testis, and thyroid andmore specific types of cancer such as acute lymphoblastic andmyeloblastic leukemia, Wilm's tumor, neuroblastoma, soft tissue sarcoma,Hodgkin's and non-Hodgkin's lymphomas, and bronchogenic carcinoma may beinhibited with a combination of one or more of the above oncolytics anda compound of this invention.

The biological activity of the compounds of the present invention wasevaluated employing an initial screening assay, which rapidly andaccurately measured the activity of the tested compound in inhibitingMRP1 or MDR1. Assays useful for evaluating this reversing capability arewell known in the art See, e.g., T. McGrath, et al., BiochemicalPharmacology, 1989; D. Marquardt and M. S. Center, Cancer Research,52:3157, 1992; D. Marquardt, et al., Cancer Research, 50:1426, 1990; andCole, et. al., Cancer Research, 54: 5902-5910, 1994.

Assay for Reversal of MRP1-Mediated Doxorubicin Resistance andMDR1-Mediated Vincristine Resistance: HL60/ADR and HL60/VCR arecontinuous cell lines, which were selected for doxorubicin andvincristine resistance respectively by culturing HL60, a human acutemyeloblastic leukemia cell line, in increasing concentrations ofdoxorubicin or vincristine until a highly resistant variant was attained

HL60/ADR and HL60/VCR cells were grown in RPMI 1640 (Gibco) containing10% fetal bovine serum (FBS) and 250 μg/ml GENTAMICIN™ (Sigma). Cellswere harvested; washed twice with assay medium (same as culture media);counted; and diluted to 2×10⁵ cells/ml in assay medium. Fiftymicroliters of cells were aliquoted into wells of a 96 well tissueculture plate. One column of each 96 well plate served as a negativecontrol and received assay medium containing no cells.

Test compounds and reference compounds were dissolved in dimethylsulfoxide (DMSO) at a concentration of 5 mM. Samples were diluted to 20μM in assay medium and 25 μl of each test compound was added to 6 wells.Assay standards were run in quadruplicate. Twenty-five microliters of0.4% DMSO was added to four wells as a solvent control. Assay media wasadded to all wells to achieve a final volume of 100 μl per well.

The plates were incubated at 37° C. for 72 hours in a humidifiedincubator with a 5% carbon dioxide atmosphere. Cell viability andvitality was measured by oxidation of a tetrazolium salt using standardconditions. The plates were incubated for 3 hours at 37° C. Absorbancewas determined at 490 nm using a microtitre plate reader.

The ability of a test compound to reverse the resistance of HL60/ADR andHL60/VCR cells to doxorubicin was determined by comparison of theabsorbance of the wells containing a test compound in addition to theoncolytic (doxorubicin) with the absorbance of wells containing theoncolytic without a test compound. Controls were used to eliminatebackground and to ensure the results were not artifactual. The resultsof the assay are expressed as percent inhibition of cell growth. Theoncolytic alone at the tested concentration does not usually inhibit thegrowth of HL60/ADR or HL60/VCR cells.

Representative compounds of formula I demonstrated a significant effectin reversing the MRP1 multiple drug resistance. Many of the compoundsshowed very significant enhancement of activity in combination with theoncolytic agent as opposed to the oncolytic agent alone. In addition, alarge majority of the compounds tested displayed a significant degree ofselective inhibition of the HL60/ADR cell line over the HL60/VCR cellline.

When administering an oncolytic in practicing the methods of thisinvention, the amount of oncolytic employed will be variable. It shouldbe understood that the amount of the oncolytic actually administeredwill be determined by a physician, in the light of the relevantcircumstances, including the condition to be treated, the chosen routeof administration, the actual oncolytic administered, the age, weight,and response of the individual patient (mammal), and the severity of thepatient's symptoms. Of course, the amount of oncolytic administeredshould be decided and closely monitored by that patient's physician.After deciding on the oncolytic or oncolytics to employ, “ThePhysician's Desk Reference®”, published by Medical Economics Company atMontvale, N.J. 07645-1742, is a helpful resource to the physician indeciding on amounts of the oncolytic to administer and is updatedannually.

Preferred formulations, and the methods of this invention employingthose formulations, are those which do not contain an oncolytic. Thus,it is preferred to administer the compounds of this invention separatelyfrom the oncolytic. The oncolytics mentioned in this specification arecommercially available and may be purchased in pre-formulated formssuitable for the methods of this invention.

The compounds of formula I alone, or optionally in combination with anoncolytic, are usually administered in the form of pharmaceuticalformulations. These formulations can be administered by a variety ofroutes including oral, rectal, transdermal, subcutaneous, intravenous,intramuscular, and intranasal. Such formulations are prepared in amanner well known in the pharmaceutical art and comprise at least oneactive compound of formula I.

The present invention also includes methods employing pharmaceuticalformulations, which contain, as the active ingredient, the compounds offormula I, and optionally an oncolytic, associated with pharmaceuticalcarriers. In making the formulations of the present invention the activeingredient(s) is usually mixed with an excipient, diluted by anexcipient, or enclosed within such a carrier which can be in the form ofa capsule, sachet, paper or other container. When the excipient servesas a diluent, it can be a solid, semi-solid, or liquid material, whichacts as a vehicle, carrier or medium for the active ingredient. Thus,the formulations can be in the form of tablets, pills, powders,lozenges, sachets, cachets, elixirs, suspensions, emulsions, solutions,syrups, aerosols (as a solid or in a liquid medium), ointmentscontaining for example up to 10% by weight of the active compound, softand hard gelatin capsules, suppositories, sterile injectable solutions,and sterile packaged powders.

In preparing a formulation, it may be necessary to mill the activecompound(s) to provide the appropriate particle size prior to combiningwith the other ingredients. If the active compound(s) is substantiallyinsoluble, it ordinarily is milled to a particle size of less than 200mesh. If the active compound(s) is substantially water soluble, theparticle size is normally adjusted by milling to provide a substantiallyuniform distribution in the formulation, e.g., about 40 mesh.

Some examples of suitable excipients include lactose, dextrose, sucrose,sorbitol, mannitol, starches, gum acacia, calcium phosphate, alginates,tragacanth, gelatin, calcium silicate, microcrystalline cellulose,polyvinylpyrrolidone, cellulose, water, syrup, and methyl cellulose. Theformulations can additionally include: lubricating agents such as talc,magnesium stearate, and mineral oil; wetting agents; emulsifying andsuspending agents; preserving agents such as methyl- andpropylhydroxybenzoates; sweetening agents; and flavoring agents. Theformulations of the invention can be formulated so as to provide quick,sustained or delayed release of the active ingredient afteradministration to the patient by employing procedures known in the art.

The formulations are preferably formulated in a unit dosage form, eachdosage containing from about 5 to about 100 mg, more usually about 10 toabout 30 mg, of each active ingredient. The term “unit dosage form”refers to physically discrete units suitable as unitary dosages forhuman subjects and other mammals, each unit containing a predeterminedquantity of active material calculated to produce the desiredtherapeutic effect, in association with a suitable pharmaceuticalexcipient

The compounds of formula I are effective over a wide dosage range. Forexample, dosages per day normally fall within the range of about 0.5 toabout 30 mg/kg of body weight In the treatment of adult humans, therange of about 1 to about 15 mg/kg/day, in single or divided dose, isespecially preferred However, it will be understood that the amount ofthe compound actually administered will be determined by a physician, inthe light of the relevant circumstances, including the condition to betreated, the chosen route of administration, the actual compoundadministered, the age, weight, and response of the individual patient,and the severity of the patient's symptoms, and therefore the abovedosage ranges are not intended to limit the scope of the invention inany way. In some instances dosage levels below the lower limit of theaforesaid range may be more than adequate, while in other cases stilllarger doses may be employed without causing any harmful side effect,provided that such larger doses are first divided into several smallerdoses for administration throughout the day.

For preparing solid formulations such as tablets the principal activeingredient(s) is mixed with a pharmaceutical excipient to form a solidpreformulation composition containing a homogeneous mixture of acompound of the present invention. When referring to thesepreformulation compositions as homogeneous, it is meant that the activeingredient(s) is dispersed evenly throughout the formulation so that theformulation may be readily subdivided into equally effective unit dosageforms such as tablets, pills and capsules. This solid preformulation isthen subdivided into unit dosage forms of the type described abovecontaining from 0.1 to about 500 mg of the active ingredient of thepresent invention.

The tablets or pills of the present invention may be coated or otherwisecompounded to provide a dosage form affording the advantage of prolongedaction. For example, the tablet or pill can comprise an inner dosage andan outer dosage component, the latter being in the form of an envelopeover the former. The two components can be separated by enteric layer,which serves to resist disintegration in the stomach and permit theinner component to pass intact into the duodenum or to be delayed inrelease. A variety of materials can be used for such enteric layers orcoatings, such materials including a number of polymeric acids andmixtures of polymeric acids with such materials as shellac, cetylalcohol, and cellulose acetate.

The novel formulations which are liquid forms may be incorporated foradministration orally or by injection and include aqueous solutions,suitably flavored syrups, aqueous or oil suspensions, and flavoredemulsions with edible oils such as cottonseed oil, sesame oil, coconutoil, or peanut oil, as well as elixirs and similar pharmaceuticalvehicles.

Formulations for inhalation or insufflation include solutions andsuspensions in pharmaceutical, aqueous or organic solvents, or mixturesthereof, and powders. The liquid or solid formulations may containsuitable pharmaceutical excipients as described supra. Preferably theformulations are administered by the oral or nasal respiratory route forlocal or systemic effect. Compositions in preferably pharmaceuticalsolvents may be nebulized by use of inert gases. Nebulized solutions maybe breathed directly from the nebulizing device or the nebulizing devicemay be attached to a facemask, tent, or intermittent positivepressure-breathing machine. Solution, suspension, or powder formulationsmay be administered, preferably orally or nasally, from devices, whichdeliver the formulation in an appropriate manner.

Another preferred formulation employed in the methods of the presentinvention employs transdermal delivery devices (“patches”). Suchtransdermal patches may be used to provide continuous or discontinuousinfusion of the compounds of the present invention in controlledamounts. The construction and use of transdermal patches for thedelivery of pharmaceutical agents is well known in the art See, e.g.,U.S. Pat. No. 5,023,252, issued Jun. 11, 1991, herein incorporated byreference. Such patches may be constructed for continuous, pulsatile, oron demand delivery of pharmaceutical agents.

Frequently, it will be desirable or necessary to introduce thepharmaceutical formulation to the brain, either directly or indirectly.Direct techniques usually involve placement of a drug delivery catheterinto the host's ventricular system to bypass the blood-brain barrier.One such implantable delivery system, used for the transport ofbiological factors to specific anatomical regions of the body, isdescribed in U.S. Pat. No. 5,011,472, issued Apr. 30, 1991, which isherein incorporated by reference.

Indirect techniques, which are generally preferred, usually involveformulating the compositions to provide for drug latentiation by theconversion of hydrophilic drugs into lipid-soluble drugs or prodrugs.Latentiation is generally achieved through blocking of the hydroxy,carbonyl, sulfate, and primary amine groups present on the drug torender the drug more lipid soluble and amenable to transportation acrossthe blood-brain barrier. Alternatively, the delivery of hydrophilicdrugs may be enhanced by intra-arterial infusion of hypertonicsolutions, which can transiently open the blood-brain barrier.

We claim:
 1. A compound of formula I:

where: A is

or

Y is —E—C(O)R¹ or —E—NR²R³; E is a bond or —CH₂—; R¹ is independently ateach occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈ cycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted heterocycle, or NR²R⁴; R² is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, (C₁-C₆ alkyl)-aryl, or aryl; R³ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, C₁-C₄ alkoxy,optionally substituted heterocycle, optionally substituted C₃-C₈cycloalkyl, optionally substituted C₆-C₁₀ bicycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, C(O)C(O)R⁹, C(O)R⁵, or R² and R³,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle; R⁴ is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, C₁-C₄ alkoxy, optionally substitutedC₃-C₈ cycloalkyl, optionally substituted C₆-C₁₀ bicycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, or R² and R⁴, together with the nitrogen to which they areattached, combine to form an optionally substituted N-heterocycle; R⁵ isindependently at each occurrence C₁-C₆ alkyl, C₁-C₆ alkoxy, (C₁-C₄alkoxy)-aryl, (C₁-C₄ alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃,optionally substituted (C₁-C₄ alkyl)-(C₃-C₈ cycloalkyl), optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl,diphenylmethyl, optionally substituted (C₁-C₄ alkyl)—CO-aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, optionally substituted (C₁-C₄ alkyl)-phenoxy,(CH₂)_(t)C(R⁶)(R⁷)N(R⁶)(R⁸), or NR²R⁴; t is 0, 1, 2, 3, or 4; R⁶ isindependently at each occurrence hydrogen or C₁-C₆ alkyl; R⁷ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈cycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, or optionally substituted heterocycle; R⁸ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, optionallysubstituted C₃-C₈ cycloalkyl, optionally substituted C₆-C₁₀bicycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, optionally substituted (C₁-C₄ alkyl)-heterocycle,optionally substituted heterocycle, C(O)OR⁹, C(O)R¹⁰, or R⁶ and R⁸,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle; R⁹ is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, C₃-C₈ cycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, oroptionally substituted heterocycle; R¹⁰ is independently at eachoccurrence C₁-C₆ alkyl, C₁-C₆ alkoxy, (C₁-C₄ alkoxy)-aryl, (C₁-C₄alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃, optionally substituted (C₁-C₄alkyl)-(C₃-C₈ cycloalkyl), optionally substituted (C₁-C₄ alkyl)-aryl,optionally substituted aryl, diphenylmethyl, optionally substituted(C₁-C₄ alkyl)—CO-aryl, optionally substituted (C₁-C₄ alkyl)-heterocycle,optionally substituted heterocycle, or optionally substituted (C₁-C₄alkyl)-phenoxy; or a pharmaceutical salt thereof; wherein: optionallysubstituted alkyl refers to a C₁-C₄ alkyl unsubstituted or substitutedfrom 1 to 3 times with halo, C₁-C₄ alkanol, NH₂, or hydroxy; optionallysubstituted (C₁-C₄ alkyl)-aryl refers to an optionally substituted aryllinked through an optionally substituted C₁-C₄ alkyl; optionallysubstituted (C₁-C₄ alkyl)—CO-aryl refers to an optionally substitutedaryl linked through a carbonyl and an optionally substituted C₁-C₄alkyl, optionally substituted (C₁-C₄ alkyl)-heterocycle refers tooptionally substituted heterocycle linked through an optionallysubstituted C₁-C₄ alkyl, optionally substituted (C₁-C₄ alkyl)-phenoxyrefers to an unsubstituted or substituted phenoxy linked through anoptionally substituted C₁-C₄ alkyl; optionally substituted aryl refersto an aryl group optionally substituted from 1 to 5 times independentlywith C₁-C₆ alkyl, halo, hydroxy, trifluoromethyl, C₁-C₆ alkoxy,benzyloxy, or trifluoromethoxy; optionally substituted C₆-C₁₀bicycloalkyl refers to a C₆-C₁₀ bicycloalkyl group optionallysubstituted from 1 to 5 times independently with C₁-C₆ alkyl, halo,hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy;optionally substituted C₃-C₈ cycloalkyl refers to a C₃-C₈ cycloalkyloptionally substituted once with a phenyl, substituted phenyl, hydroxy,or C₁-C₄ alkoxy; optionally substituted heterocycle refers to aheterocycle ring optionally substituted 1 or 2 times independently witha C₁-C₆ alkyl, halo, benzyl, phenyl, trifluoromethyl, or an oxo group;heterocycle refers to stable aromatic and non-aromatic 5- and 6-memberedrings containing from 1 to 3 heteroatoms selected from the groupconsisting of nitrogen, oxygen, and sulfur, said rings being optionallybenzofused; N-heterocycle refers to a nitrogen containing heterocyclelinked through a nitrogen atom; optionally substituted N-heterocyclerefers to a heterocycle ring, linked through the nitrogen atom,optionally substituted 1 or 2 times independently with a C₁-C₆ alkyl,halo, benzyl, phenyl, trifluoromethyl, or an oxo group; substitutedphenoxy refers to a phenoxy group wherein the phenyl is optionallysubstituted from 1 to 5 times independently with C₁-C₆ alkyl, halo,hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy;and substituted phenyl refers to a phenyl group substituted from 1 to 5times independently with C₁-C₆ alkyl, halo, hydroxy, trifluoromethyl,C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy.
 2. A method of inhibitingMRP1 in a mammal which comprises administering to a mammal in needthereof an effective amount of a compound of formula I:

where: A is

or

Y is —E—C(O)R¹ or —E—NR²R³; E is a bond or —CH₂—; R¹ is independently ateach occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈ cycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted heterocycle, or NR²R⁴; R² is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, (C₁-C₆ alkyl)-aryl, or aryl; R³ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, C₁-C₄ alkoxy,optionally substituted heterocycle, optionally substituted C₃-C₈cycloalkyl, optionally substituted C₆-C₁₀ bicycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, C(O)C(O)R⁹, C(O)R⁵, or R² and R³,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle; R⁴ is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, C₁-C₄ alkoxy, optionally substitutedC₃-C₈ cycloalkyl, optionally substituted C₆-C₁₀ bicycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, or R² and R⁴, together with the nitrogen to which they areattached, combine to form an optionally substituted N-heterocycle; R⁵ isindependently at each occurrence C₁-C₆ alkyl, C₁-C₆ alkoxy, (C₁-C₄alkoxy)-aryl, (C₁-C₄ alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃,optionally substituted (C₁-C₄ alkyl)-(C₃-C₈ cycloalkyl), optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl,diphenylmethyl, optionally substituted (C₁-C₄ alkyl)—CO-aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, optionally substituted (C₁-C₄ alkyl)-phenoxy,(CH₂)_(t)C(R⁶)(R⁷)N(R⁶)(R⁸), or NR²R⁴; t is 0, 1, 2, 3, or 4; R⁶ isindependently at each occurrence hydrogen or C₁-C₆ alkyl; R⁷ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈cycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, or optionally substituted heterocycle; R⁸ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, optionallysubstituted C₃-C₈ cycloalkyl, optionally substituted C₆-C₁₀bicycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, optionally substituted (C₁-C₄ alkyl)-heterocycle,optionally substituted heterocycle, C(O)OR⁹, C(O)R¹⁰, or R⁶ and R⁸,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle; R⁹ is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, C₃-C₈ cycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, oroptionally substituted heterocycle; R¹⁰ is independently at eachoccurrence C₁-C₆ alkyl, C₁-C₆ alkoxy, (C₁-C₄ alkoxy)-aryl, (C₁-C₄alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃, optionally substituted (C₁-C₄alkyl)-(C₃-C₈ cycloalkyl), optionally substituted (C₁-C₄ alkyl)-aryl,optionally substituted aryl, diphenylmethyl, optionally substituted(C₁-C₄ alkyl)—CO-aryl, optionally substituted (C₁-C₄ alkyl)-heterocycle,optionally substituted heterocycle, or optionally substituted (C₁-C₄alkyl)-phenoxy; or a pharmaceutical salt thereof; wherein: optionallysubstituted alkyl refers to a C₁-C₄ alkyl unsubstituted or substitutedfrom 1 to 3 times with halo, C₁-C₄ alkanol, NH₂, or hydroxy; optionallysubstituted (C₁-C₄ alkyl)-aryl refers to an optionally substituted aryllinked through an optionally substituted C₁-C₄ alkyl; optionallysubstituted (C₁-C₄ alkyl)—CO-aryl refers to an optionally substitutedaryl linked through a carbonyl and an optionally substituted C₁-C₄alkyl; optionally substituted (C¹-C₄ alkyl)-heterocycle refers tooptionally substituted heterocycle linked through an optionallysubstituted C₁-C₄ alkyl; optionally substituted (C₁-C₄ alkyl)-phenoxyrefers to an unsubstituted or substituted phenoxy linked through anoptionally substituted C₁-C₄ alkyl; optionally substituted aryl refersto an aryl group optionally substituted from 1 to 5 times independentlywith C₁-C₆ alkyl, halo, hydroxy, trifluoromethyl, C₁-C₆ alkoxy,benzyloxy, or trifluoromethoxy; optionally substituted C₆-C₁₀bicycloalkyl refers to a C₆-C₁₀ bicycloalkyl group optionallysubstituted from 1 to 5 times independently with C₁-C₆ alkyl, halo,hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy;optionally substituted C₃-C₈ cycloalkyl refers to a C₃-C₈ cycloalkyloptionally substituted once with a phenyl, substituted phenyl, hydroxy,or C₁-C₄ alkoxy; optionally substituted heterocycle refers to aheterocycle ring optionally substituted 1 or 2 times independently witha C₁-C₆ alkyl halo, benzyl phenyl, trifluoromethyl, or an oxo group;heterocycle refers to stable aromatic and non-aromatic 5- and 6-memberedrings containing from 1 to 3 heteroatoms selected from the groupconsisting of nitrogen, oxygen, and sulfur, said rings being optionallybenzofused; N-heterocycle refers to a nitrogen containing heterocyclelinked through a nitrogen atom; optionally substituted N-heterocyclerefers to a heterocycle ring, linked through the nitrogen atom,optionally substituted 1 or 2 times independently with a C₁-C₆ alkyl,halo, benzyl, phenyl, trifluoromethyl, or an oxo group; substitutedphenoxy refers to a phenoxy group wherein the phenyl is optionallysubstituted from 1 to 5 times independently with C₁-C₆ alkyl, halo,hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy;and substituted phenyl refers to a phenyl group substituted from 1 to 5times independently with C₁-C₆ alkyl, halo, hydroxy, trifluoromethyl,C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy.
 3. A method of inhibitinga resistant neoplasm, or a neoplasm susceptible to resistance, in amammal which comprises administering to a mammal in need thereof aneffective amount of a compound of formula I:

where: A is

or

Y is —E—C(O)R¹ or —E—NR²R³; E is a bond or —CH₂—; R¹ is independently ateach occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈ cycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted heterocycle, or NR²R⁴; R² is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, (C₁-C₆ alkyl)-aryl, or aryl; R³ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, C₁-C₄ alkoxy,optionally substituted heterocycle, optionally substituted C₃-C₈cycloalkyl, optionally substituted C₆-C₁₀ bicycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, C(O)C(O)R⁹, C(O)R⁵, or R² and R³,together with the nitrogen to which they are attached, combine to forman optionally substituted N-heterocycle; R⁴ is independently at eachoccurrence hydrogen, C₁-C₆ alkyl, C₁-C₄ alkoxy, optionally substitutedC₃-C₈ cycloalkyl, optionally substituted C₆-C₁₀ bicycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, or R² and R⁴, together with the nitrogen to which they areattached, combine to form an optionally substituted, N-heterocycle; R⁵is independently at each occurrence C₁-C₆ alkyl, C₁-C₆ alkoxy, (C₁-C₄alkoxy)-aryl, (C₁-C₄ alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃,optionally substituted (C₁-C₄ alkyl)-(C₃-C₈ cycloalkyl), optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl,diphenylmethyl, optionally substituted (C₁-C₄ alkyl)—CO-aryl, optionallysubstituted (C₁-C₄ alkyl)-heterocycle, optionally substitutedheterocycle, optionally substituted (C₁-C₄ alkyl)-phenoxy,(CH₂)_(t)C(R⁶)(R⁷)N(R⁶)(R⁸), or NR²R⁴; t is 0, 1, 2, 3, or 4; R⁶ isindependently at each occurrence hydrogen or C₁-C₆ alkyl; R⁷ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈cycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, or optionally substituted heterocycle; R⁸ isindependently at each occurrence hydrogen, C₁-C₆ alkyl, optionallysubstituted C₃-C₈ cycloalkyl, optionally substituted C₆-C₁₀bicycloalkyl, optionally substituted (C₁-C₄ alkyl)-aryl, optionallysubstituted aryl, optionally substituted (C₁-C₄ alkyl)-heterocycle,optionally substituted heterocycle, C(O)OR⁹, C(O)R⁹, C(O)R¹⁰ or R⁶ andR⁸, together with the nitrogen to which they are attached, combine toform an optionally substituted N-heterocycle; R⁹ is independently ateach occurrence hydrogen, C₁-C₆ alkyl, C₃-C₈ cycloalkyl, optionallysubstituted (C₁-C₄ alkyl)-aryl, optionally substituted aryl, oroptionally substituted heterocycle; R¹⁰ is independently at eachoccurrence C₁-C₆ alkyl, C₁-C₆ alkoxy, (C₁-C₄ alkoxy)-aryl, (C₁-C₄alkoxy)-heterocycle, (C₁-C₄ alkoxy)—SiCH₃, optionally substituted (C₁-C₄alkyl)-(C₃-C₈ cycloalkyl), optionally substituted (C₁-C₄ alkyl)-aryl,optionally substituted aryl, diphenylmethyl, optionally substituted(C₁-C₄ alkyl)—CO-aryl, optionally substituted (C₁-C₄ alkyl)-heterocycle,optionally substituted heterocycle, or optionally substituted (C₁-C₄alkyl)-phenoxy; or a pharmaceutical salt thereof; wherein: optionallysubstituted alkyl refers to a C₁-C₄ alkyl unsubstituted or substitutedfrom 1 to 3 times with halo, C₁-C₄ alkanol, NH₂, or hydroxy; optionallysubstituted (C₁-C₄ alkyl)-aryl refers to an optionally substituted aryllinked through an optionally substituted C₁-C₄ alkyl; optionallysubstituted (C₁-C₄ alkyl)—CO-aryl refers to an optionally substitutedaryl linked through a carbonyl and an optionally substituted C₁-C₄alkyl; optionally substituted (C₁-C₄ alkyl)-heterocycle refers tooptionally substituted heterocycle linked through an optionallysubstituted C₁-C₄ alkyl; optionally substituted (C₁-C₄ alkyl)-phenoxyrefers to an unsubstituted or substituted phenoxy linked through anoptionally substituted C₁-C₄ alkyl; optionally substituted aryl refersto an aryl group optionally substituted from 1 to 5 times independentlywith C₁-C₆ alkyl, halo, hydroxy, trifluoromethyl, C₁-C₆ alkoxy,benzyloxy, or trifluoromethoxy; optionally substituted C₆-C₁₀bicycloalkyl refers to a C₆-C₁₀ bicycloalkyl group optionallysubstituted from 1 to 5 times independently with C₁-C₆ alkyl, halo,hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy;optionally substituted C₃-C₈ cycloalkyl refers to a C₃-C₈ cycloalkyloptionally substituted once with a phenyl, substituted phenyl, hydroxy,or C₁-C₄ alkoxy; optionally substituted heterocycle refers to aheterocycle ring optionally substituted 1 or 2 times independently witha C₁-C₆ alkyl, halo, benzyl, phenyl, trifluoromethyl, or an oxo group;heterocycle refers to stable aromatic and non-aromatic 5- and 6-memberedrings containing from 1 to 3 heteroatoms selected from the groupconsisting of nitrogen, oxygen, and sulfur, said rings being optionallybenzofused; N-heterocycle refers to a nitrogen containing heterocyclelinked through a nitrogen atom; optionally substituted N-heterocyclerefers to a heterocycle ring, linked through the nitrogen atom,optionally substituted 1 or 2 times independently with a C₁-C₆ alkyl,halo, benzyl, phenyl, trifluoromethyl, or an oxo group; substitutedphenoxy refers to a phenoxy group wherein the phenyl is optionallysubstituted from 1 to 5 times independently with C₁-C₆ alkyl, halo,hydroxy, trifluoromethyl, C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy;and substituted phenyl refers to a phenyl group substituted from 1 to 5times independently with C₁-C₆ alkyl, halo, hydroxy, trifluoromethyl,C₁-C₆ alkoxy, benzyloxy, or trifluoromethoxy; in combination with aneffective amount of one or more oncolytic agents.
 4. The methodaccording to claim 3 where the mammal is a human.
 5. The methodaccording to claim 4 where the oncolytic(s) is selected from:doxorubicin, daunorubicin, epirubicin, vincristine, and etoposide. 6.The method according to claim 4 where the neoplasm is of the Wilm'stype, bladder, bone, breast, lung(small-cell), testis, or thyroid or theneoplasm is associated with acute lymphoblastic and myeloblasticleukemia, neuroblastoma, soft tissue sarcoma, Hodgkin's andnon-Hodgkin's lymphomas, and bronchogenic carcinoma.
 7. A pharmaceuticalformulation comprising a compound of formula I as defined in claim 1 inadmixture with one or more pharmaceutical carriers, diluents, orexcipients therefor.
 8. A pharmaceutical according to claim 7 whichcomprises one or more oncolytic agents.
 9. The formulation according toclaim 8 where the oncolytic(s) is selected from: doxorubicin,daunorubicin, epirubicin, vincristine, and etoposide.